The principle and structure used for a full-color e-paper using three elementary colors

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Fuji Xerox Co Ltd showed an electrophoretic type electronic paper (e-paper) that realizes color display without using a color filter on the opening day of SID 2012, which runs from June 3 to 8, 2012, in Boston, the US.

Because the e-paper does not use a color filter, it can realize a brighter and more vivid display, the company said (thesis number 8.4).

The color e-paper (electrophoretic display) developed by Fuji Xerox realizes color display by moving colored particles for each color. To control each color of the particles, the company designed them so that the threshold value (electric field) of electrophoresis becomes different for each color. The e-paper has two substrates, and the color of a particle drawn to the front board can be seen.

In addition to the colored particles, white-color particles are placed between the two substrates. And the white-color particles do not move even when an electric field is generated between the substrates. Therefore, a white color can be displayed by drawing all the colored particles to the back board.

The prototype showed at SID 2012 displayed colors by moving red and cyan colored particles up and down. It has a screen size of 5 inches, pixel count of 600 x 800, resolution of 200dpi, gradation of four, reflectance of 30% and contrast ratio of 10:1. It uses amorphous silicon (Si) TFTs for the back board.

Though the prototype uses two elementary colors to realize color display, Fuji Xerox is currently developing a full-color e-paper using three elementary colors. The company has already developed a cell (pixel) using cyan, magenta and yellow colored particles and confirmed a color gamut wider than that of newspaper.